The overall goal of this project is to understand the role of lipid peroxidation products in inducing cardiac injury and dysfunction caused by chronic hemodynamic stress. Our working hypothesis is that the effects of reactive oxygen species, generated in these hearts, are in part mediated by 4-hydroxyalkenals produced as a result of lipid peroxidation. We propose that modification of myocardial proteins by these aldehydes is a significant source of cardiac injury and dysfunction induced by chronic hemodynamic stress and therefore, metabolic detoxification of these aldehydes diminishes myocardial hypertrophy and heart failure. To test this hypothesis we will examine 4-hydroxyalkenal formation and metabolism in hearts subjected to transverse aortic constriction (TAC) and we will measure changes in the activity and the levels of aldehyde-metabolizing enzymes and cellular nucleophiles such as reduced glutathione and carnosine. To identify changes in aldehyde metabolism, metabolites of 4-hydroxy-trans-2-nonenal (HNE) generated in hypertrophic hearts perfused with radiolabeled HNE will be identified and quantified along with HNE metabolites generated in vivo in the blood and urine of mice subjected to TAC. To determine the role of aldehyde metabolism in regulating cardiac injury and dysfunction induced by pressure overload, we will examine whether genetic deletion of aldose reeducates (which catalyzes the reductive metabolism of aldehydes) or cardiospecific overexpression of carnosine synthase (which generates the aldehyde-quenching dipeptide - carnosine in the heart) affects myocardial injury and dysfunction after TAC. To examine the mechanism by which aldehydes induce myocardial injury, we will examine whether exposure to HNE triggers autophagy; whether the pathways of autophagy activated by HNE are also stimulated by TAC; and whether changes in aldehyde metabolism via aldose reductase and carnosine alter autophagic responses in hypertrophic and failing hearts. Completion of this project will lead to a better understanding of the role of oxidative stress in myocardial hypertrophy and heart failure as well as other chronic conditions associated with an increase in lipid peroxidation such as diabetes, atherosclerosis and cardiovascular aging. Our results could provide novel insights into the mechanisms by which hemodynamic stress induces myocardial injury and dysfunction and how these changes could be attenuated. We expect that these findings will have wide mechanistic, prognostic and therapeutic implications for diagnosis, management, and treatment of pathological hypertrophy and heart failure.